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What do we learn from Azimuthal Anisotropy Measurements @ RHIC and the LHC Roy A. Lacey Chemistry Dept., Stony Brook University. Take home m essage - PowerPoint PPT Presentation
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What do we learn from Azimuthal Anisotropy Measurements @ RHIC and
the LHCRoy A. Lacey
Chemistry Dept., Stony Brook University
1 WWND13 @ Squaw Valley, Feb. 2013, Roy A. Lacey, Stony Brook University
Take home message The scaling (pT, ε, R, ∆L, etc) properties of azimuthal anisotropy
measurements at RHIC & the LHC, inform crucial mechanistic insights and constraints for characterization of the QGP?
2
RHIC (0.2 TeV) LHC (2.76 TeV)Power law dependence (n ~ 0.2) increase ~ 3.3 Multiplicity density increase ~ 2.3 <Temp> increase ~ 30%
Lacey et. al, Phys.Rev.Lett.98:092301,2007
Relevant questions: How do the transport coefficients evolve with T?
Any indication for a change in coupling close to To?
ˆ, , ,s sc qs
WWND13 @ Squaw Valley, Feb. 2013, Roy A. Lacey, Stony Brook University
Energy scan
Why RHIC and LHC Measurements?
The energy density lever arm
Why Azimuthal Anisotropy Measurements?
This implies very specific scaling properties for flow and jet suppression (respectively), which can be tested experimentally
Scaling validation provide important insights, as well as straightforward probes of transport coefficients
WWND13 @ Squaw Valley, Feb. 2013, Roy A. Lacey, Stony Brook University
pT <
3 -
4 G
eV/c
Flow
pT > 8 -10 GeV/c
Jet suppression
3
Eccentricity driven& acoustic
3-4 < pT < 8-10 GeV/c
Path length (∆L) driven
More
suppression
Lesssuppression
TransitionRegion
Flow and Jet suppression are linked to Geometry & the interactions in the QGP
4
Geometric Quantities for scaling
A B
Geometric fluctuations included Geometric quantities constrained by multiplicity density.
~L R
L R
*cosn nn
Phys. Rev. C 81, 061901(R) (2010)
arXiv:1203.3605
σx & σy RMS widths of density distribution
WWND13 @ Squaw Valley, Feb. 2013, Roy A. Lacey, Stony Brook University
Scaling properties of high-pT anisotropy
WWND13 @ Squaw Valley, Feb. 2013, Roy A. Lacey, Stony Brook University 5
6 WWND13 @ Squaw Valley, Feb. 2013, Roy A. Lacey, Stony Brook University
Jet suppression Probe
AAAA
binary AA pp
YieldR ( , )N YieldTp L
2( , ) [1 2 ( )cos(2 )]T TYield p v p
2
AA 20
AA 2
(90 , ) 1 2 ( )( , )(0 , ) 1 2 ( )
oT T
TT T
R p v pR p LR p v p
Suppression (∆L) – pp yield unnecessary
Jet suppression drives azimuthal anisotropy at high pT with specific scaling properties on L,
Suppression (L)
, Phys.Lett.B519:199-206,2001
For Radiative Energy loss:
0
LcIT eI
Modified jet
Moresuppression
Lesssuppression
Fixed Geometry
Path length(related to collision
centrality)
Specific pT and centrality dependencies – Do they scale?
7 WWND13 @ Squaw Valley, Feb. 2013, Roy A. Lacey, Stony Brook University
0 5 10
v 2
0.00
0.05
0.10
0.15
0.20
0.25
10 - 20%
Au+Au @ 0.2 TeV
pT (GeV/c)0 5 10
20 - 30%
0 5 100.00
0.05
0.10
0.15
0.20
0.2530 - 40%
High-pT v2 measurements - PHENIX
pT dependence
Centrality dependence
High-pT v2 measurements - CMS
Specific pT and centrality dependencies – Do they scale?
8
arXiv:1204.1850
pT dependence
Centralitydependence
WWND13 @ Squaw Valley, Feb. 2013, Roy A. Lacey, Stony Brook University
9
High-pT v2 scaling - LHC
v2 follows the pT dependence observed for jet quenchingNote the expected inversion of the 1/√pT dependence
arXiv:1203.3605
WWND13 @ Squaw Valley, Feb. 2013, Roy A. Lacey, Stony Brook University
2
AA 20
AA 2
(90 , ) 1 2 ( )( , )(0 , ) 1 2 ( )
oT T
TT T
R p v pR p LR p v p
pT-1/2 (GeV/c)-1/2
0.2 0.3 0.4 0.5
v 2
0.0
0.1
0.2
10 - 20 (%)20 - 3030 - 40
0.2 0.3 0.4 0.5
v 2/L
(fm-1
)
0.0
0.2
0.4
Au+Au @ 0.2 TeV
10
∆L Scaling of high-pT v2 – LHC & RHIC
Combined ∆L and 1/√pT scaling single universal curve for v2 Constraint for εn
arXiv:1203.3605
WWND13 @ Squaw Valley, Feb. 2013, Roy A. Lacey, Stony Brook University
Npart
0 100 200 300
v 2/L
0.0
0.5
v 2
0.0
0.1
0.2 6 < pT < 9 (GeV/c)pT > 9
pT-1/2 (GeV/c)-1/2
0.2 0.4 0.6
v 2/L
0.0
0.2
0.4
10 - 20 (%)20 - 3030 - 40
Au+Au @ 0.2 TeV
11 WWND13 @ Squaw Valley, Feb. 2013, Roy A. Lacey, Stony Brook University
∆L Scaling of high-pT v2 - RHIC
Combined ∆L and 1/√pT scaling single universal curve for v2
Constraint for εn
(pTJet)-1/2 (GeV/c)-1/2
0.05 0.10 0.15
v 2Jet
0.00
0.05
0.10
10-20 (%)20-30 30-40 40-50
Pb+Pb @ 2.76 TeV
12
Jet v2 scaling - LHC
v2 for reconstructed Jets follows the pT dependence for jet quenchingSimilar magnitude and trend for Jet and hadron v2 after scaling
WWND13 @ Squaw Valley, Feb. 2013, Roy A. Lacey, Stony Brook University
pT-1/2 (GeV/c)-1/2
0.1 0.2 0.3
v 2
-0.05
0.00
0.05
0.10
0.15Jet - ATLASHadron - CMS
pT-1/2 (GeV/c)-1/2
0.1 0.2 0.3
v 2
-0.05
0.00
0.05
0.10
0.15Jet - ATLASHadrons - CMSHadrons - scaled (z ~ .62)
ATLAS
10-20%
13
Jet suppression from high-pT v2
Jet suppression obtained directly from pT dependence of v2 Compatible with the dominance of radiative energy loss
arXiv:1203.3605
2( , ) [1 2 ( )cos(2 )]T TN p v p
2
AA 20
AA 2
(90 , ) 1 2 ( )( , )(0 , ) 1 2 ( )
oT T
v TT T
R p v pR p LR p v p
Rv2 scales as 1/√pT , slopes encodes info on αs and q̂
WWND13 @ Squaw Valley, Feb. 2013, Roy A. Lacey, Stony Brook University
RAA scales as 1/√pT ; slopes (SpT) encode info on αs and q L and 1/√pT scaling single universal curveCompatible with the dominance of radiative energy loss
14
arXiv:1202.5537
pT scaling of Jet Quenching
ˆ
, Phys.Lett.B519:199-206,2001
WWND13 @ Squaw Valley, Feb. 2013, Roy A. Lacey, Stony Brook University
15
Extracted stopping power
2
ˆ ~ 0.75 RHICGeVq
fm
Phys.Rev.C80:051901,2009
2
ˆ ~ 0.56 LHCGeVq
fm
obtained from high-pT v2 and RAA [same αs] similar - medium produced in LHC collisions less opaque! (note density increase from RHIC to LHC)
arXiv:1202.5537 arXiv:1203.3605
Conclusion similar to those of Liao, Betz, Horowitz, Stronger coupling near Tc?
qRHIC > qLHCˆqLHC ˆ
WWND13 @ Squaw Valley, Feb. 2013, Roy A. Lacey, Stony Brook University
L (fm)0.5 1.0 1.5 2.0
ln(R
AA)
-1.5
-1.0
-0.5
0.0D (prompt)6 - 12 GeV/c
Pb+Pb @ 2.76 TeV
ALICE
Consistent obtained
16 WWND13 @ Squaw Valley, Feb. 2013, Roy A. Lacey, Stony Brook University
qLHC ˆ
Heavy quark suppression
Scaling properties of low pT anisotropy
WWND13 @ Squaw Valley, Feb. 2013, Roy A. Lacey, Stony Brook University 17
The Flow Probe
s/
P ² Bj
, , /s, f, Ts fc
20
3
1 1
~ 5 45
TBj
dER dy
GeVfm
18
Idealized Geometry
2 2
2 2
y x
y x
Crucial parametersActual collision profiles are not smooth,
due to fluctuations!Initial Geometry characterized by many
shape harmonics (εn) drive vn
Initial eccentricity (and its attendant fluctuations) εn drive momentum anisotropy vn with specific scaling properties
22, exp 03
tT t k k Ts T
Acoustic viscous modulation of vn
Staig & Shuryak arXiv:1008.3139
Isotropic p
Anisotropic p
WWND13 @ Squaw Valley, Feb. 2013, Roy A. Lacey, Stony Brook University
Yield() =2 v2 cos[2(Y2]
Characteristic n2 viscous damping for harmonics
Crucial constraint for η/s
Associate k with harmonic n /k n R
19 WWND13 @ Squaw Valley, Feb. 2013, Roy A. Lacey, Stony Brook University
2 gR n
εn drive momentum anisotropy vn with modulation
22, exp 03
tT t k k Ts T
Scaling expectation
2( )expn T
n
v pn
Acoustic Modulation
2
2 2
( ) exp ( 4)( )
n T n
T
v p nv p
t R ln n
n
vR
Characteristic centrality (1/R) viscous damping for a given harmonic
Crucial constraint for η/s
Particle Distribution
Note that vn is related to v2
Characteristic n2 viscous damping and 1/(pT)α dependence Crucial constraint for η/s and δf
20 WWND13 @ Squaw Valley, Feb. 2013, Roy A. Lacey, Stony Brook University
2expn
n
vn
Is viscous hydrodynamic flow acoustic?
pT (GeV/c)0 1 2 3
(p T)
0.00
0.05
0.10
0.15
0.20
0.25
0.304s = 1.25(pT)-1/2
4s = 1.25 & f~pT1.5
20-30%Hydro - Schenke et al.
Note: the hydrodynamic response to the initial geometry [alone] is included
ATLAS-CONF-2011-074
21
High precision double differential Measurements are pervasiveDo they scale?
WWND13 @ Squaw Valley, Feb. 2013, Roy A. Lacey, Stony Brook University
vn(ψn) Measurements - ATLAS
22 WWND13 @ Squaw Valley, Feb. 2013, Roy A. Lacey, Stony Brook University
Acoustic Scaling
Characteristic n2 viscous damping validated Characteristic 1/(pT)α dependence of β validated Constraint for η/s
2( ) expn T
n
v p n
23 WWND13 @ Squaw Valley, Feb. 2013, Roy A. Lacey, Stony Brook University
Acoustic Scaling
Characteristic n2 viscous damping validated Characteristic 1/(pT)α dependence of β validated Constraint for η/s
24 WWND13 @ Squaw Valley, Feb. 2013, Roy A. Lacey, Stony Brook University
Acoustic Scaling
Straightforward constraint for eccentricity models /2
2n
n Tv p v
25 WWND13 @ Squaw Valley, Feb. 2013, Roy A. Lacey, Stony Brook University
1/R (fm-1)0.0 0.5 1.0 1.5
ln(v
2/2)
-2.0
-1.6
-1.2
-0.8
-0.4
0.0
0.4 1.7 1.1 0.7
pT (GeV/c)ATLAS Pb+Pb @ 2.76 TeV
1/R (fm-1)0.0 0.5 1.0 1.5
ln(v
2/ 2)
-2.0
-1.6
-1.2
-0.8
-0.4
0.0
0.4 1.7 1.1 0.7
ATLAS p+Pb @ 5.02 TeV
pT (GeV/c)ATLAS Pb+Pb @ 2.76 TeV
Acoustic Scaling
ln n
n
vR
Characteristic 1/R viscous damping validated A further constraint for η/s
Centrality – 5-50%
26 WWND13 @ Squaw Valley, Feb. 2013, Roy A. Lacey, Stony Brook University
1/R (fm-1)0.0 0.5 1.0 1.5
ln(v
2/ 2)
-2.0
-1.6
-1.2
-0.8
-0.4
0.0
0.4 1.79 1.19 0.79
pT (GeV/c)PHENIX Au+Au @ 0.2 TeV
1/R (fm-1)0.0 0.5 1.0 1.5
ln(v
2/ 2)
-2.0
-1.6
-1.2
-0.8
-0.4
0.0
0.4 1.79 1.19 0.79
ATLAS p+Pb @ 5.02 TeV
pT (GeV/c)PHENIX Au+Au @ 0.2 TeV
Acoustic Scaling
ln n
n
vR
Characteristic 1/R viscous damping validated A further constraint for η/s
27 WWND13 @ Squaw Valley, Feb. 2013, Roy A. Lacey, Stony Brook University
Flow increases from RHIC to LHC Sensitivity to EOS increase in <cs>
Proton flow blueshifted [hydro prediction] Role of radial flowRole of hadronic re-
scattering?
Flow increases from RHIC to LHC
28
β Important constraint for η/s and δf
WWND13 @ Squaw Valley, Feb. 2013, Roy A. Lacey, Stony Brook University
Constraint for η/s & δf
<η/s> ~ 1/4π at RHIC; 25-30% increase for LHC
3
1.2ˆLHC
Ts q
arXiv:1301.0165 3
~ 1.2ˆRHIC
Ts q
Phys.Rev. C80 (2009) 051901
Remarkable scaling have been observed for both Flow and Jet Quenching
They lend profound mechanistic insights, as well as New constraints forestimates of the transport and thermodynamic coefficients!
29
RAA and high-pT azimuthal anisotropy stem from the same energy loss mechanism
Energy loss is dominantly radiative
RAA and anisotropy measurements give consistent estimates for <ˆq >
RAA for D’s give consistent estimates for <ˆq >
The QGP created in LHC collisions is less opaque than that produced at RHIC
Flow is acousticFlow is pressure driven Obeys the dispersion relation
for sound propagation Flow is partonic
exhibits scalingConstraints for:
initial geometry small increase in η/s from
RHIC (~ 1/4π) to LHC
What we learn?
/2 n, 2, /2
vv ( ) ~ v or ( )
nn q T q n
q
KEn
Summary
WWND13 @ Squaw Valley, Feb. 2013, Roy A. Lacey, Stony Brook University
End
30WWND13 @ Squaw Valley, Feb. 2013, Roy A. Lacey, Stony Brook University
31
Flow Saturates for 39 - 200 GeV
WWND13 @ Squaw Valley, Feb. 2013, Roy A. Lacey, Stony Brook University
No sizeable beam energy dependence observed for v2 and v3 for each particle
species
flow saturates for 39-200 GeV Soft EOS
32
Flow is partonic @ the LHC
Scaling for partonic flow validated after accounting for proton blueshift
Larger partonic flow at the LHC
KET (GeV)
0.5 1.0 1.5 0.5 1.0 1.5 0.5 1.0 1.5
10-20%
0.5 1.0 1.50.00
0.05
0.10
0.1520-30% 30-40% 40-50%
0.5 1.0 1.5
v 2/nq
0.00
0.05
0.10
0.15
Kp
Pb+Pb @ 2.76 TeV 05-10%
WWND13 @ Squaw Valley, Feb. 2013, Roy A. Lacey, Stony Brook University
33 WWND13 @ Squaw Valley, Feb. 2013, Roy A. Lacey, Stony Brook University
For partonic flow, quark number scaling expected single curve for identified particle species vn
Is flow partonic?
/2 n2 /2
vExpectation: v ( ) ~ v or ( )
nn T n
q
KEn Note species dependence for all vn
34 WWND13 @ Squaw Valley, Feb. 2013, Roy A. Lacey, Stony Brook University
Acoustic Scaling
Increase of s2 for most central collisions is to be expected
ln n
n
vR
35
Flow @ RHIC and the LHC
WWND13 @ Squaw Valley, Feb. 2013, Roy A. Lacey, Stony Brook University
Multiplicity-weighted PIDed flow results reproduce inclusive charged hadron flow
results at RHIC and LHC respectively
Charge hadron flow similar @ RHIC & LHC